The present invention relates generally to surgical attachment of prosthetic devices. More particularly, the present invention relates to the use of a heating device to decrease the curing or setting time of a bone cement used to secure a prosthetic device to a patient.
Prostheses are widely used in medicine to replace or supplement various body parts, including joints and limbs. Typically, the prosthesis is attached to the patent during a surgical procedure performed in an operating room. During the surgical procedure, a prosthesis receiving location is prepared in the patient where the prosthesis will be attached. The prosthesis is positioned in the receiving location and a bone cement, such as polymethyl methacrylate cement (PMMA) that binds the prosthesis to the patient""s bone, is applied to the prosthesis. The prosthesis is then held in place while the cement cures. This curing time can be relatively long depending upon the type of bone cement used and other factors. Unfortunately, the surgeon and the operating room staff often are required to wait until the cement cures before continuing with the surgery or any other matters they need to tend to. Due to the substantial costs involved in running an operating room, the cost of this down time can be significant. Some bone cement manufacturers have changed the various composite materials used to create the cement in an effort to reduce cure time. Although this approach has been shown to improve upon the cure time of the cement, the change in composition often compromises its ability to adhere to the prosthesis and demonstrate long term clinical stability.
What is needed, therefore, is an improved method and apparatus for securing a prosthesis in a patient.
The above described deficiencies in the prior art are improved upon by a device for reducing the curing time of a bone cement used to secure a heat-conductive prosthesis inside a patient constructed in accordance with the present invention. The device is a battery powered device that is configured to be hand-held. The device includes a heater for being placed into contact with the prosthesis. The heater has a tip that is designed to couple heat from the heater to the prosthesis. The heater tip produces heat in response to an electrical power signal that is provided to the metal prosthesis through conduction. A power supply generates the electrical power signal and provides the electrical power signal to the heater tip. A trigger activates the power supply to send the electrical power signal to the heater tip when it is depressed. The tip of the heater may be a sterilized heater tip that is designed to be disposed of after each use. In one embodiment, the tip of the heater is removable from the heater and replaceable with a tip from a set of tips wherein each of the tips in the set of tips is configured to mate with a different type of prosthesis. In another embodiment, the heater tip is not removable from the heater. The heater has a temperature gauge that provides an indication of the temperature of the heater tip and an adjustable heater control that allows an operator of the device to select the amount of heat produced by the heater tip.
The present invention is also directed toward a method of securing a metal prosthesis in a patient. The method begins with the securing of the metal prosthesis in a desired position in the patient with a heat-curable bone cement. A heat source is applied to the metal prosthesis such that heat is transferred from the metal prosthesis to the heat-curable cement. The temperature of the applied heat source is monitored to insure that an excessive amount of heat is not applied to the heat-conductive prosthesis. In one embodiment, heat is applied to the metal prosthesis by applying heated air to the surface of the prosthesis. In another embodiment, heat is applied by applying a heated liquid to the metal prosthesis. In yet another embodiment, a heated pad is used to apply heat to the area in which the prosthesis is implanted. Preferably, the heat source is a heater having a heater socket for receiving a sterilized heater tip from a set of sterilized heater tips and a heater tip is installed in the heater socket that is configured to couple with the particular type of metal prosthesis being implanted in the patient. The heat source is then applied to the metal prosthesis for a predetermined amount of time. The heat source is removed from the prosthesis after the cement is sufficiently cured and the used heater tip is discarded.
The above described embodiments provide a number of advantages over the prior art. Most importantly, they reduce the required time for the PMMA cement to cure and, thereby, reduce the time and costs associated with the implantation surgery. The use of disposable sterilized tips allows these advantages to be realized without the need for costly sterilization procedures or the risk of harm to the patient. Furthermore, the provision of a tip socket on the heater allows a heater tip to be selected based upon the particular procedure to be performed. Therefore, the present invention represents a substantial improvement upon the prior art.